The invention relates to a vertical axis and transversal flow nautical propulsor with continuous self-orientation of the blades.
More particularly, the invention relates to a nautical propulsor of the above kind able to satisfy, in the different operation conditions, the maximum fluid mechanic efficiency.
As is well known, mechanic propulsion by means of horizontal axis propellers is the most common propulsive apparatus, in view of its constructive simplicity and of the many different kinds available and hydrodynamically tested.
However, the use of this kind of apparatus has some unfavorable aspects, that can be summarized as follows:
1) limited optimum range (good efficiency only for specific speeds); PA1 2) creation of visible vortical wakes, and high values for the centrifugal and tangential forces created (reveals the presence of remarkable loss of energy); and PA1 3) penalization of the performances due to the hull effect (high discrepancies of the features of the propeller insulated and mounted on the hull).
The need for reducing these unfavorable aspects leads to the exploration of new, additional or substitute propulsion solutions.
Particularly, in the case of uses requiring a high level of silentness, attention has focused on the development of vertical axis propulsors, having a blade axis perpendicular with respect to the advancement direction. The flow transversely crosses the blade supporting disc and is slightly deviated; the final result on the fluid is not different with respect to the one due to sea mammal anal fins, that instinctively carry out during the motion the same kinematic functions (a result of adaptive evolution in the environment).
During tests carried out within a naval basin on these propulsive systems, aspects came out that directly influence in a determining way the performances of the new kind of propulsor and that remarkably increase its fluid mechanic performances and its flexibility.
Among the most important, the following can be mentioned: a formation effect between the blades; the number of the blades; the maximum impact angles; the ratio between the orbital ray of the blade supporting disc and the maximum chord of the blade; the chord to blade lengthening ratio; and the configuration of the hydrodynamic profile of the blade.
A first type of vertical blade propulsor is shown in U.S. Pat. No. 1,823,169, which discloses a vertical blade propulsor in which the head motors move fixedly with the rotor plate.
The vertical axis propulsors presently known have a plurality of blades, rotating upon themselves, supported by a rotating disc, the motion of the rotating disc and the rotation of the blade being due to a single motor and to a mechanical linkage assembly. An example of such propulsors is disclosed in FR-A-2 099 178.
Generally speaking, the control of the blade orientation is operated by mechanical kinematisms on the bases of angular positioning curves having an established shape an fixed during the rotation.
Furthermore, the blades are characterized by a symmetrical profile which does not allow one to obtain an optimum efficiency for any position and situation that could be encountered.
Moreover, in view of their intrinsic features, the known vertical axis propulsors cannot be employed for immersion naval means.
The known vertical axis propulsors are of the cycloidal or trocoidal kind.